Yeast to Sourdough Conversion Calculator

How This Tool Works

This calculator converts yeast-based bread recipes to sourdough by replacing commercial yeast with sourdough starter. The conversion is more complex than simply swapping ingredients - you must account for the flour and water already in the starter. Most sourdough starters are 100% hydration (equal weights of flour and water), so if you use 100g of starter, you're adding 50g flour and 50g water to your recipe. The calculator automatically subtracts these amounts from your recipe's flour and water to maintain the correct dough consistency.

The typical conversion uses starter at 20% of total flour weight (e.g., 100g starter for 500g total flour). This provides enough leavening power while maintaining good flavor. However, sourdough requires significantly longer fermentation times (2-3x longer than commercial yeast) because wild yeasts are less concentrated. The slower fermentation develops the complex, tangy flavors that make sourdough special, but requires patience and planning. Always use active, bubbly starter at peak activity for best results.

Conversion Guidelines

• Starter Amount: Typically 20% of total flour weight (e.g., 100g starter for 500g flour)
• Starter Hydration: Assumes 100% hydration (equal parts flour and water) - most common
• Flour Adjustment: Subtract half the starter weight from recipe flour (100g starter = -50g flour)
• Water Adjustment: Subtract half the starter weight from recipe water (100g starter = -50g water)
• Timing: Sourdough requires 2-3x longer fermentation than commercial yeast (plan for 3-5 hours vs. 1.5 hours)
• Starter Activity: Use starter at peak activity (doubled in size, bubbly, passes float test)
• Temperature: Optimal fermentation temperature is 24-27°C for sourdough
• No Additional Yeast: Remove all commercial yeast from the recipe - starter provides the leavening

Sourdough Conversion Best Practices

• Feed Starter First: Feed your starter 4-12 hours before using to ensure it's at peak activity
• Float Test: Drop a small piece of starter in water - if it floats, it's active and ready
• Adjust Hydration: If your starter isn't 100% hydration, adjust calculations accordingly
• Plan Extra Time: Sourdough takes much longer - plan your schedule accordingly
• Temperature Control: Maintain consistent temperature (24-27°C) for predictable rising times
• Watch for Doubling: Use visual cues (dough doubles) rather than time alone
• Stretch and Fold: Sourdough benefits from stretch-and-fold technique during bulk fermentation
• Cold Fermentation: Consider overnight cold fermentation in refrigerator for enhanced flavor

Key Differences: Yeast vs. Sourdough

• Rising Time: Sourdough takes 2-3x longer (3-5 hours vs. 1.5 hours for first rise)
• Flavor: Sourdough develops complex, tangy flavors that commercial yeast doesn't produce
• Texture: Sourdough often has a chewier, more open crumb structure
• Starter Maintenance: Sourdough requires regular feeding and maintenance
• Predictability: Commercial yeast is more predictable; sourdough varies with starter activity
• Acidity: Sourdough is more acidic, which can affect flavor and preservation
• Nutrition: Sourdough may have slightly better digestibility due to longer fermentation

FAQ

• How do I convert a yeast recipe to sourdough?
  Replace the yeast with sourdough starter (typically 20% of total flour weight). Adjust the flour and water in your recipe to account for the flour and water already in the starter. Sourdough starter is usually 100% hydration (equal parts flour and water).
• How much sourdough starter should I use?
  A common ratio is 20% starter by total flour weight. For example, if your recipe uses 500g flour, use 100g of active sourdough starter. This provides enough leavening power while maintaining good flavor.
• Do I need to adjust flour and water when using sourdough?
  Yes! Since starter contains flour and water, you need to subtract those amounts from your recipe. If using 100g of 100% hydration starter, subtract 50g flour and 50g water from your recipe amounts.
• How long does sourdough take to rise compared to yeast?
  Sourdough typically takes 2-3 times longer than commercial yeast. A yeast bread that rises in 1.5 hours may take 3-5 hours with sourdough, depending on starter activity and temperature.
• What hydration should my sourdough starter be?
  Most recipes assume 100% hydration starter (equal weights of flour and water). This is the most common and easiest to work with - for example, 50g flour + 50g water = 100g starter. Some bakers prefer 80% hydration (50g flour + 40g water) or 50% hydration (50g flour + 25g water) for different characteristics. Lower hydration starters are thicker and may be easier to handle, while 100% hydration is standard and works well for most recipes. If your starter has different hydration, you'll need to adjust the flour and water calculations accordingly. Always measure your starter by weight, not volume.
• How do I know if my starter is active enough?
  An active starter should: Double in size within 4-8 hours after feeding, have lots of bubbles throughout, have a pleasant, slightly tangy smell (not sour or alcoholic), pass the float test (a small piece floats in water), and be at peak activity (use 4-12 hours after feeding). If your starter isn't active, it may need more frequent feedings, warmer temperature, or time to mature. A weak starter will result in slow or failed rising. Always use starter at peak activity for best results in bread making.
• Can I use both yeast and sourdough starter?
  Yes, you can use both (called "hybrid" bread), but it's not a true conversion. Using both gives you some sourdough flavor with faster rising times. However, for a true sourdough conversion, you should remove all commercial yeast and rely solely on the starter for leavening. Hybrid breads are a good middle ground if you want sourdough flavor but need faster results. If converting a recipe, it's better to go fully sourdough for the authentic experience, but hybrid is an option if you're short on time.
• Why is my sourdough bread not rising?
  Common reasons sourdough doesn't rise: Starter isn't active enough (feed it more frequently, ensure it's at peak), not enough starter (increase to 20-25% of flour weight), temperature too cold (sourdough needs 24-27°C), not enough time (sourdough takes 2-3x longer - be patient), over-proofed (dough collapsed), or salt added too early (salt can slow yeast activity). Make sure your starter passes the float test and is bubbly before using. Sourdough rising is slower and less dramatic than commercial yeast - watch for gradual increase in volume.
• How do I maintain my sourdough starter?
  To maintain starter: Feed regularly (daily if at room temperature, weekly if refrigerated), use equal weights of flour and water (100% hydration), discard half before feeding (or use the discard in recipes), keep at consistent temperature (room temp for active use, fridge for storage), and watch for activity (should double after feeding). For daily maintenance: Discard half, add equal weights of flour and water (e.g., 50g flour + 50g water to 50g remaining starter). For storage: Feed, then refrigerate - feed weekly when stored. Bring to room temperature and feed 2-3 times before using.